1. Field of the Invention
The present invention relates to a coil element comprising a bobbin and a coil wound around the bobbin and electrically connected to a wiring pattern formed on a printed circuit board.
2. Description of the Related Art
Conventionally, a line filter corresponding to a coil element is structured, for example, as shown in FIGS. 6 to 8. That is, as shown in these drawings, a line filter is constituted by a bobbin 2, a coil 4 wound around right and left portions of the bobbin 2 with respect to a central flange-like partition portion 3 in the bobbin 2, and a ferrite 5 attached to the bobbin 2, and terminal ends 4a of the coil 4 are connected to two metal pin terminals 6 provided in both end portion on a lower surface of the bobbin 2.
Then, a coating of the terminal end 4a of the coil 4 is removed due to a solder heat, for example, at a time of solder dipping, and the terminal end 4a of the connected coil 4 is temporarily welded to the pin terminal 6 by a solder. Thereafter, the terminal end 4a is electrically connected to a wiring pattern formed on a printed circuit board (not shown).
At this time, the pin terminal 6 is inserted to a through hole pierced in the printed circuit board and soldered on the wiring pattern of the printed circuit board, mounting of the line filter 1 to the printed circuit board is completed.
However, in this case, since it is necessary to connect the terminal end 4a of the coil 4 to the pin terminal 6, an operation therefor is very troublesome, so that there is a problem that a lot of time is required to treat the terminal end of the coil 4. Further, since it is necessary that the metal pin terminal 6 for terminating the coil 4 is provided in the bobbin 2, a cost increase is caused at that degree.
Further, a thickness of the pin terminal 6 is increased by the solder attached at a time of temporary welding, however, when the solder becomes uneven at a time of connecting the terminal end 4a of the coil 4, there is a case that only a part of the pin terminal 6 becomes abnormally thick, so that there is generated a disadvantage that it is impossible to easily insert the pin terminal 6 to the through hole when the pin terminal 6 becomes the same thickness as a diameter of the through hole in the printed circuit board side.
In order to prevent the disadvantage mentioned above, it can be considered that the diameter of the through hole in the printed circuit board side is formed larger in order to take into consideration an increased amount of the thickness of the pin terminal 6 due to the temporary welding, however, in such a case, the thickness of the pin terminal 6 becomes even when the solder attached at a time of the temporary welding in a state that the terminal end of the coil 4 is normally treated, so that a gap between the through hole to be inserted and the pin terminal 6 becomes too large. Accordingly, since a lack of solder is generated at a time of soldering the pin terminal 6 to the wiring pattern, there is generated a new problem wherein a stable soldering can not be performed, a crack is easily generated in a solder bridge, and an addition solder operation is required.
Here, with respect to the coil element, the applicant of the present invention has proposed an invention described in Japanese Utility Model No. 3045143, however, in this case, it is necessary to perform a trouble some operation such as to connect the terminal end of the coil to the terminal portion.
Accordingly, an object of the present invention is to provide a coil element which requires no troublesome treatment of a terminal end of a coil and can electrically connect to a printed circuit board in a stable manner.
In order to achieve the object mentioned above, in accordance with the present invention, there is provided a coil element having a bobbin and a coil wound around the bobbin and electrically connected to a wiring pattern formed on a printed circuit board, comprising:
a first projection and a second projection formed in the bobbin and respectively inserted to a first through hole and a second through hole pierced in the printed circuit board;
a hook portion formed in the first projection and with which a terminal end portion of the coil is hooked; and
pressing means formed in the second projection and pressing the hook portion to one side of an inner periphery of the first through hole in accordance with an insertion to the second through hole.
In accordance with the structure mentioned above, a terminal end treatment can be briefly performed only by hooking the terminal end of the coil with the hook portion of the first projection without necessity of connecting the terminal end of the coil as in the conventional manner, and further since the metal pin terminal is not required to be provided in the bobbin, it is possible to reduce a material cost.
Further, since the hook portion is pressed to one side of the inner periphery of the first through hole by the pressing means at a time of inserting the first and second projections of the bobbin to the first and second through holes of the printed circuit board after hooking the terminal end of the coil with the hook portion, it is possible to securely bring the terminal end of the coil hooked with the hook portion into contact with the wiring pattern by arranging the wiring pattern in a pressing side thereof, so that it is possible to realize a stable electric connection by a soldering or the like performed thereafter.
Further, in accordance with the present invention, the structure is characterized in that the hook portion is provided with a guide groove for the terminal end portion of the coil formed in the first projection, and a solder is applied after the terminal end portion of the coil is hooked with the guide groove.
In accordance with the structure mentioned above, since the guide groove is provided, it is possible to stably hook the terminal end of the coil without being shifted.
Further, in accordance with the present invention, the structure is characterized in that the pressing means is provided with an inclined surface formed on a side surface of the second projection, thereby pressing the hook portion to one side of the inner periphery of the first through hole and in a direction of closing to the wiring pattern due to a cooperation between the inclined surface and the inner peripheral edge of the second through hole at a time of inserting the second projection to the second through hole.
In accordance with the structure mentioned above, since the inclined surface of the second projection slides the inner peripheral edge of the second through hole at a time of inserting the second projection of the bobbin to the second through hole of the printed circuit board, it is possible to easily press the hook portion in the direction of closing to the wiring pattern due to a cooperation between the inclined surface and the inner peripheral edge of the second through hole.
Further, in accordance with the present invention, the structure is characterized in that a distance of incline of the inclined surface is set to a displacement amount for at least pressing the hook portion. In accordance with the structure mentioned above, it is possible to displace the hook portion due to the sliding operation of the inclined surface till the hook portion is just brought in to contact with the wiring pattern, at a time of inserting the second projection to the second through hole, and it is possible to stably perform a soldering operation thereafter.